Introduction. Topological physics is extensively studied in
condensed-matter physics[1]}, [2]}. A topological phase is signaled by
the emergence of topological edge states if a sample has a boundary. Now,
the target of topological physics is expanded to artificial topological
systems such as acoustic[3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, mechanical[13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}, [21]}, [22]}, [23]}, [24]}, [25]}, [26]}, [27]}, [28]}, [29]}, photonic[30]}, [31]}, [32]}, [33]}, [34]}, [35]}, [36]}, [37]} and
electric circuit[38]}, [39]}, [40]}, [41]}, [42]}, [43]}, [44]}, [45]}, [46]}, [47]}, [48]}
systems. The merit of artificial topological systems is that system
parameters can be finely controlled. In addition, it is possible to make a
small sample with clean edges.
